97 XJ Sport with multiple codes and won't shift out of 1st gear

Hello,

I recently picked up a 97 Jeep XJ AW4 NP231 HP30 & 8.8 and the Jeep is running like crap and won't shift out of 1st gear. I connected my scanner and it is returning the following codes:


P0108 (M) Map Sensor Voltage Too High MAP sensor input above maximum acceptable voltage. (Snap-on MT2500 scanner result: Map sensor voltage too high)

P0132 (M) 1/1 O2 Sensor Shorted To Voltage Oxygen sensor input voltage maintained above normal operating range (Snap-on MT2500 scanner result: Upstream O2 sensor shorthed high)

P0138 (M) 1/2 O2 Sensor Shorted To Voltage Oxygen sensor input voltage maintained above normal operating range. (Snap-on MT2500 scanner result: Downstream O2 sensor shorthed to voltage)

P0305 (M) CYLINDER #5 MISFIRE Misfire detected in cylinder #5.

P0320 (M) No RPM Signal to PCM (Crankshaft Position Sensor Signal to JTEC) A CKP signal has not been detected at the PCM. (Snap-on MT2500 scanner result: No crank reference signal at PCM)

It will drive in reverse and only in 1st until it reaches 2400 to 2600 rpm and then it boggs down and dies. My instrument cluster shows rpms when cranking and running so I really don't think that my CPS is down. Will a bad O2 sensor really affect the engine's performance?

Do any of you have any advice on what to do? or how I can test it out?

Thank you in advance

Running crappy and not shifting is usually the Throttle Position Sensor.

You can test the CPS Crankshaft Position Sensor.

Inspect the O2 sensors, wires, and connectors for damaged wires and short circuits, loose connections, and dirty connectors. A short circuit can put voltage where it should not be.

.
CPS Testing


Crankshaft Position Sensor Connector (CPS/CKP)





TESTING PROCEDURE 1991 – 2001 4.0L H.O. engines

1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C (See Image). Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.

This sounds like you have a bad O2 sensor or more likely some wiring harness damage. I would check the wiring harness for the O2 sensors near the exhaust manifold and pipe and make sure it hasn't been melted. My bet is that the sensor power bus (which powers all the sensors that use 5V power) is shorted to a few signal lines and this is confusing those signals as well as other sensors using the same power bus.

Thank you for your help. I will check them as soon as I can. I did notice that the O2 Sensor at the cat has been taped up with duct tape. I will peel it away and check there first.

This is so similar to a problem we had with my buddie's 2000. It threw about the same amount of codes. That does seem symptomatic of an oxygen sensor failing, the PCM shouldn't care what the O2 sensors are doing in reverse, so most autos run great in reverse with a bad O2 but as soon as you go forward it all goes down hill. It should freak out well before 2500 RPMs I would imagine, however.

The codes there seem numerous and only kind of connected, it runs from your emissions stuff up to engine management type stuff.

Back to my friend's 2000, we replaced TPS, CKP, IAC, and MAP sensors and it would run fine for a couple hours then go back to the same codes and run like garbage. It wound up being the IOD fuse. The fuse itself should not cause the rig to mess up like it does, it's only function is to store the time and presets for your radio and manage sleep mode for your PCM, however that was his problem.

Hope this helps

Arkansas91XJ said:

This is so similar to a problem we had with my buddie's 2000. It threw about the same amount of codes. That does seem symptomatic of an oxygen sensor failing, the PCM shouldn't care what the O2 sensors are doing in reverse, so most autos run great in reverse with a bad O2 but as soon as you go forward it all goes down hill. It should freak out well before 2500 RPMs I would imagine, however.

Click to expand...

:huh:

Anyone know if this is true? The ECU on an XJ does not even know what gear the transmission is in as far as I know, that info is only relevant to the TCU. I can't even begin to comprehend how it would matter what direction the vehicle is traveling for the ECU to pay attention to the O2 sensors.

The TCM does communicate with the PCM, even though the PCM doesn't control the TCM. They are all on that CCD bus together.

Anyway, my info may be wrong, I seem to be working more on other types of cars these days, and most other vehicles seem to ignore Oxygen sensors while in reverse. I guess I assumed it to be a trait of all OBD-II rigs.

Anyway, the point I was getting to, regardless of my story, was the IOD fuse lol

I know - I'm working on reverse engineering the stock TCU actually. I'm 99.9% sure the ECU doesn't give a rat's ass whether it's driving forward or reverse, however...

Arkansas91XJ said:

It wound up being the IOD fuse. The fuse itself should not cause the rig to mess up like it does, it's only function is to store the time and presets for your radio and manage sleep mode for your PCM, however that was his problem.

Hope this helps

Click to expand...

Can you tell me what IOD stands for and where the fuse is located?

Thanks

Ignition Off Draw

It's in your fuse box under the hood. By description, design, and FSM it shouldn't cause the ride to mess up, but it did for his.

kastein said:

I know - I'm working on reverse engineering the stock TCU actually. I'm 99.9% sure the ECU doesn't give a rat's ass whether it's driving forward or reverse, however...

Click to expand...

Make that 100 % (or 110 % for you over-achievers).

With all those sensor codes pointing to too-high voltages, I wonder if you don't actually have a bad common sensor ground somewhere.

Start by checking for loose or dirty ground terminals that connect to chassis on the firewall, near the battery tray and near the air box....